Electrically excited lasers are known from German patent specifications DE-PS 26 08 830 and DE-PS 27 35 299. In these lasers the discharge chamber is enclosed between. the wall surfaces of a waveguide. These lasers do, however, operate with customary resonators having mirrors which are either ground so as to be plane or are concavely curved, i.e. these are optically stable resonators. These waveguide lasers generally have a plurality of laser regions which are not optically interconnected and which are decoupled in particular transversely to the optical axis of the resonators.
This plurality of laser regions arranged side by side has the disadvantage that the laser beams coupled out of these regions cannot be advantageously combined with one another since the laser regions do not operate exactly phase-coupled and so the entire laser arrangement does not oscillate in a unified manner which is required for commercial use, in particular for good focusing.
This disadvantage is particularly serious when a diffusion-cooled waveguide laser of this type is intended to produce high power output. In order to overcome the resulting loss of power it is imperative to construct the discharge chamber so that it has as large a volume as possible and the waveguide so that it is relatively broad since the thickness of the waveguide cannot be increased in order not to lose the advantageous optical and thermal properties of the waveguide.